Interactive PTY: tab completion does nothing in the VM shell

Summary

Tab completion does nothing in the interactive VM shell. Pressing Tab (or writing a raw \t byte to the PTY) produces no completion, no candidate list, and no bell — the byte is simply consumed.

This is server-side, not a terminal-client problem: it reproduces by writing \t straight to the PTY with no browser involved.

Reproduction

import { AgentOs } from "@rivet-dev/agentos-core";
import common from "@agentos-software/common";

const vm = await AgentOs.create({ software: [common] });
const shell = await vm.terminal.open({ cols: 80, rows: 24 });
const id = shell.shellId;
let buf = "";
vm.onShellData(id, (e) => { buf += Buffer.from(e?.data ?? e).toString("utf8"); });
await new Promise((r) => setTimeout(r, 1500));

buf = "";
await vm.terminal.write(id, "una\t");
await new Promise((r) => setTimeout(r, 3000));
console.log(JSON.stringify(buf));

Observed: "una" — the echoed prefix only.

Expected (bash/zsh behavior): completes to uname, since /opt/agentos/bin/uname exists and is on PATH.

Possible cause

software/coreutils/native/crates/cmd-sh/Cargo.toml enables both interactive backends:

brush-shell = { version = "0.3.0", default-features = false, features = ["reedline", "minimal"] }

The adjacent comment describes minimal as "an explicit opt-out backend", so if minimal is the backend actually selected on wasm32-wasip1, no completer is wired up. That matches the observation that Tab produces nothing at all rather than a failed or empty completion attempt.

If that is the cause, this may be a feature-flag/backend-selection fix rather than a change to brush itself.

Note

The Cargo manifest pins brush-shell 0.3.0, but the live prompt renders as sh-0.4$. Worth confirming which build is actually being executed before digging in — it may indicate the running sh is not the pinned one.

Related

• #1579 — merged; revived brush-interactive as a reedline integration test, which would be the place to assert completion behavior.

Start with software/coreutils/native/crates/cmd-sh/Cargo.toml and confirm which brush-shell backend and build are actually used on wasm32-wasip1; also verify whether the running shell matches the pinned 0.3.0 dependency. Review the revived brush-interactive reedline integration test from #1579. Done means writing a tab byte in the VM shell produces the expected uname completion and the behavior is covered by an integration test.